1. Field of the Invention
The present invention relates to an apparatus and a method for switching channels in a digital broadcast system.
2. Description of the Related Art
A digital broadcasting system refers to a television broadcasting system that provides broadcasting by compressing multimedia signals into a digital format by which information signals are written in codes. A conventional analogue television broadcasting system has been able to transmit one image on one channel, but use another channel to broadcast voice. In addition to this, the digital broadcasting system can transmit a plurality of images and voices in one channel while compressing multimedia information without quality degradation. As a result, the digital broadcasting system has an advantage of setting about 4 to 8 channels in a frequency bandwidth corresponding to a single analogue broadcast channel of the prior art. In addition, the use of a computer facilitates multimedia information transmission, and enables information demanded by a viewer to be transmitted via a digital transmission system. The digital broadcasting system compresses images and voices as well as modulates several signals, in which communication and PCs adopt equal compression and multiple-modulation techniques.
In order to provide better services to audience, such a digital broadcasting system transmits additional System Information (SI) such as channel information together with multimedia data compressed by a Moving Picture Experts Group (MPEG) technique. In particular, by containing program information currently being broadcasted or to be broadcasted to users in such system information, it is possible to provide Electronic Program Guide (EPG) services.
An open cable digital broadcasting system according to, for example, known standards in Korea, generally includes a digital broadcast transmitting system and a digital broadcast receiving system such as a set top box.
The digital broadcast transmission system may include a digital broadcasting server or an audio/video server, a system information server, a conditional access server and a Cable Modem Termination System (CMTS).
The audio/video server is a device for compressing multimedia signals to transmit. The system information server is adapted to transmit service information of a broadcast channel, and the conditional access server allows only specific users to access specific or all contents. The CMTS is a cable head end, converting cable modem data into Internet data packets.
The digital broadcast receiving system is a device to interpret and display broadcasting and service information transmitted from the head end installed in the digital broadcast transmission system for the purpose of cable TV or cable modem services provided to subscribers. The digital broadcast receiving system may generally include a cable modem, a Moving Picture Experts Group (MPEG) host and a conditional access unit.
The cable modem connects a PC (personal computer) to a cable TV line, enabling the PC to download data up to a rate of about 10 Mbps. The MPEG host serves to separate and demodulate multimedia data out of data received from the MPEG host, and then display it via a display unit such as a TV. The MPEG host interprets service information of input data to display it. The conditional access unit receives encoded contents from the digital broadcast transmission system, and only if their receipt is authenticated, restores the encoded contents into common images.
In a method of switching broadcast channels in a conventional digital broadcast system in which a user switches channels by inputting channel number personally, the user inputs channel number personally by using an interface such as a remote controller including Arabic number keys. An EPG (electronic program guide) module of the MPEG host of the digital broadcast receiving system, upon receiving channel number, switches channels by performing controlled extraction selectively to a signal corresponding to the input channel number.
In a method of switching broadcast channels in a conventional digital broadcast system in which a user switches channels by using an EPG, the digital broadcast transmission system sends service information to the digital broadcast receiving system. Service information contains various information related with broadcast services such as channel number, channel name, program name, broadcast date, broadcast startup time, program identification number and program description. The EPG module of the digital broadcast receiving system writes a channel guide by collecting service information to output the channel guide via the display unit such as a TV. The user can select a program to watch from service information displayed on the display unit. In this case, the EPG module controls a tuner to selectively extract a signal corresponding a channel selected by the user.
As described above, channel switching by a user personally inputting channel number has a problem in that users have to memorize channel numbers. Furthermore, there is inconvenience in that users also have to memorize channel numbers whenever channel numbers are changed according to areas and times of digital broadcasting services. In the meantime, EPG channel switching requires users to examine service information of a number of digital broadcast channels one by one, thereby disadvantageously consuming a long-term period.